The invention relates to a vehicle headlight, comprising a housing and modulatable light or IR radiation sources arranged within the housing, and comprising an interface for connection to an external vehicle processor, according to the preamble of claim 1.
All light or IR radiation sources radiating into the external region of a vehicle shall be understood as vehicle headlamps here and below, i.e. both front headlamps and rear lights which are used for illumination or signalling. Vehicle headlights are increasingly used for this purpose in which LEDs (light-emitting diodes) are arranged on module supports in the manner of a matrix as light or IR radiation sources. If the LEDs used in this case are additionally operated with AFL (adaptive forward lighting) technology, the illumination profile of the vehicle headlight can be varied, wherein the LED modules can be dimmed to a differently strong extent by means of a vehicle processor depending on the desired illumination profile. Changes in the illumination profile of the vehicle headlight during travel, i.e. during travel through curves, changing weather conditions or recognised objects at the edge of the road will also be referred to below as a dynamic illumination profiles. The desired illumination profile can be selected by means of respective sensors for example which determine information from the ambient environment of the vehicle and respectively control the vehicle headlights via the vehicle processor.
The LED module for the front headlamp for example mixes white light by a combination of several wavelengths. These wavelengths are generated partly indirectly by blue LEDs made of gallium nitride (GaN) and a converter layer, and partly directly by yellow LEDs made of aluminium indium gallium phosphide (AlInGaP). The LED modules for the rear lights or brake lights generate wavelengths around 700 nm by red LEDs made of semiconductors such as aluminium gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminium gallium indium phosphide (AlGaInP) or gallium phosphide (GaP). The beam formation of the LED modules is usually supported by plastic lenses and mirror reflectors.
Furthermore, efforts were made to equip vehicles with so-called “time of flight” (ToF) cameras. The ToF cameras concern cameras which not only record a 2D image but also measure depth information for each recorded pixel. Depth information is understood as information on the distances between the individual objects of a scene and the ToF camera. ToF cameras are also known as active cameras since they are equipped with their own light source, which will also be referred to below as ToF light source. The light emitted by this light source is reflected on objects of a scene to be recorded and thus reaches the detection region of the image sensor of the camera as backscatter radiation. The depth information is determined from the reflected light via the runtime and phase difference measurements.
Possibilities for using the ToF technology in vehicles are described in US 2008039914 A1, WO 2008154736 A1, DE 102006025020 A1 and DE 102006044794 A1.
The light sources are usually LEDs which emit modulated light. The light is usually emitted by means of a ToF modulator in the megahertz range in an OOK (On-Off Keying) modulated manner (e.g. with 20 MHz), and is thus emitted into the field of vision of the own image sensor. The reflected light components (photons) are received by the camera sensor and used for calculating the distance of the reflected object. These depth data are subsequently available for applications in addition to the greyscale image. Infrared LEDs or laser diodes are used for illumination in most applications. PMD image sensors with 352×288 pixels (QVGA resolution) are currently usually used as image sensors. The image sensors must be supplied with the OOK signal according to the shutter principle, which signal is also used synchronously for triggering the ToF light source. The image sensor subsequently supplies an analog differential signal, from which the depth information per pixel can be calculated by using several sequential image recordings in the ToF camera processor. The power dissipation of conventional ToF cameras lies in the range of 10 W to 100 W and is relevantly determined by the power of the ToF light source and the triggering signal.
An application of ToF technology in automotive engineering which is fit for day-to-day use and suitable for series production has not yet been produced. On the one hand, there are technical difficulties because the light source required for the ToF camera causes a considerable additional need for more power for the power supply of the vehicle and a respective need for increased cabling. Furthermore, the image sensor and the light source of the ToF camera are arranged separately from each other in the vehicle for practical reasons, i.e. in that the light source is positioned in the region of the radiator grille in order to avoid dazzling oncoming vehicle drivers, and the image sensor in the region of the windscreen. This means additional cabling work for the ToF system itself because the high-frequency modulation signal cannot be transmitted via the existing vehicle interfaces to the ToF light source. The cabling and the transmission electronics are further subject to the stringent EMC regulations on vehicle electronics. Furthermore, the separate mounting position of the two parts further limits the purpose due to the low amount of overlapping of the fields of vision.
In addition to the aforementioned technical difficulties, there are further also practical problems such as those caused by the soiling of a ToF light source arranged in the region of the radiator grille, as well as logistical problems in the development, production and maintenance of the vehicle because several different vehicle regions (e.g. radiator grille and bonnet, passenger compartment and windscreen, tailgate or bumper) are affected and thus different divisions of the manufacturer are involved in the integration and approval of the respective components.